Fuel injection pump with improved return flow conduit

ABSTRACT

In an injection internal combustion engine having a fuel injection pump, wherein the fuel passes by gravity flow from a supply container through an admission conduit to the injection pump, at least one return flow conduit separate from the admission conduit is provided for superfluous fuel which has entered the pump which has not been injected, this return conduit leading from the injection pump to the supply container, and being equipped with a valve which is preferably of the non-return type, but which, when it is in its seated position, allows a small flow of fuel between the return flow conduit and the injection pump. The superfluous or non-injected fuel thus does not pass back into the admission conduit. The valve construction may be of various types so long as it permits the small flow of fuel when the valve member is in its seated or relatively closed position.

United States Patent 1191 1111 3,871,345 Hatz et al. Mar. 18, 1975 [54] FUEL INJECTION PUMP WITH IMPROVED 468,307 7/1937 United Kingdom 123/139 R RETURN FLOW CONDUIT [75] Inventors: Ernst Ilatz; Erhard Oertel, both of primary Emminer Char|eS Myhre Ruhstorf Germany Assistant ExaminerTony Argenbright [73] Assignee; Motorenfabrik Hatz KG, Ruhstorf, Attorney, Agent, or FirmLarson, Taylor & Hinds Germany [22] Filed: Aug. 7, 1973 [57] ABSTRACT [211 App]. No.: 386,283

In an injection internal combustion engine having a 30 Foreign Application priority Data fuel in ection pump, where n the fuel passes by gravity Aug [6 1972 Germany 2240123 flow from a supply container through an admission 4 1973 Germany 2316687 conduit to the injection pump, at least one return flow conduit separate from the admission conduit is pro- [52] U 5 Cl 123/139 AF 123/139 AA 123/139 R vided for superfluous fuel whichthas entered the pump [51] I 59/44 which has not been injected, this return conduit lead- [58] Field of Search... 123/139 R 139 AA 139 AF' ing fmm W Pump SUPPIY miner, r 417/499 and being equipped with a valve which 15 preferably of the non-return type, but which, when it is in its seated [56] References Cited position, allows a small flow of fuel between the return flow conduit and the injection pump. The superfluous I UNITED T T PATENTS or non-injected fuel thus does not pass back into the l,8l Salisbury R admission conduit The valve construction may be of 2,333,944 11/1943 Lieberherr 123/139 R Various types so long as it permits the Small flow of 5:32; 7 fuel when the valve member is in its seated or rela- 2:83l:433 4/1958 Seifert et al. 417/499 x WI/closed FOREIGN PATENTS OR APPLlCATIONS 10 Claims, 7 Drawing Figures 176,120. 6/1935 Switzerland 123/139 R l 7 i 2a 26 i4 PATENTED W1 8 7 sum 2 (1f 2 FUEL INJECTION PUMP WITH IMPROVED RETURN FLOW CONDUIT FIELD OF THE INVENTION This invention relates to an injection internal combustion engine with at least one fuel injection pump, wherein the fuel passes by gravity flow from a supply container through an admission conduit to the injection pump.

BACKGROUND AND SUMMARY In internal combustion engines of this character only a fraction of the quantity of fuel which is withdrawn by the injection pump from the supply container at each stroke is forwarded to the injection nozzle and is combusted. The major part of the inducted quantity of fuel is caused to return back into the suction conduit system of the pump before and/or after the effective piston stroke has taken place. This arrangement has the disadvantage however that the returning fuel is subjected to an undesirable turbulence and bubble formation in the suction conduit system, and in addition is heated up by the injection pump, which is very hot during the operation, and communicates this heat to the fresh inflowing fuel. A further disagreeable feature is that in the case of systems which have a gravity flow of the fuel from the supply tank to the pump, i.e., no additional fuel supply pump, detachable and consequently complicated and expensive components (annular joint pieces, hollow screws, or the like) have to be provided in the conduit system to enable the whole system to be vented before the operation commences by opening a number of these components and thereby making the engine ready to start. It is an object of the present invention to avoid the disadvantages of these known constructions and provide a fuel conducting system which has improved flow properties, contributes effectively to the cooling of the fuel, offers the possibility of automatic venting, and, not least, permits the use of simple, smooth and thus inexpensive fuel conduits and thereby provides a basis for economic mass production.

These objects are met in accordance with the present invention by the fact that at least one return flow conduit separate from the admission conduit is provided for superfluous fuel which has not been injected, this leading from the injection pump to the supply container and being equipped with a valve which, when it is in its seated position, allows a small flow of fuel between the return flow conduit and the injection pump.

In the case of injection internal combustion engines having a piston injection pump, the piston of which is arranged in a piston bush provided with a return flow duct, the excess fuel not injected passing out through the return flow duct into a collecting chamber of the pump, in a particularly advantageous arrangement the return flow conduit is connected to the collecting chamber and the opening thereof into the chamber is disposed approximately opposite the return flow duct in the piston bush. In this respect it is advantageous to place said valve, e.g., a non-return valve, in the immediate vicinity of the mouth of the return flow conduit.

In a preferred form of the invention the non-return valve comprises a valve ball which cooperates with a valve seat in the return flow conduit and has a plurality of narrow ducts, at least one of which at any time provides a small conducting connection between the return flow conduit and the collecting chamber when the valve ball is applied against the valve seat.

A similar conducting connection can be obtained by the provision of a few grooves or the like of small cross section in the seat of the valve ball.

A form of non-return valve which is particularly suitable for mass production is acquired in accordance with a further feature of the invention by making the valve ball operate without the assistance of a restoring spring and allowing it to cooperate with a stop in the return flow conduit limiting the movement of this ball. It is of particular advantage in this instance to make the valve ball of synthetic material.

DESCRIPTION OF THE DRAWINGS Embodiments of the invention are illustrated in the accompanying drawings, in which FIG. 1 gives a diagrammatic illustration of the admission system of the injection pump.

FIGS. 2 and 3 show part of the pump in longitudinal section and in plan with part in section.

FIGS. 4 and 5 illustrate the non-return valve on a larger scale and in two different embodiments.

FIGS. 6 and 7 illustrate a further embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The conduit system of the injection pump is diagrammatically illustrated in FIG. 1. The fuel flows from the fuel tank 10, which is mounted at an elevated level, through an admission conduit 12, to the injection pump 14 through a fuel filter 16 of known type. The unused superfluous fuel flows back through a return conduit 18 to the tank 10 in a way which will be described later. The injection pump 14 drives the quantity of fuel to be injected through a pressure conduit 20 to the injection nozzle (not shown) of the internal combustion engine.

The injection pump 14 is a known form of so-called insertion pump, in which a body 14a extending downwards therefrom has arranged therein a piston bush 22 with a pump piston 24 movable longitudinally therein. The pump is fastened through the agency of flange 14f (FIG. 3), which has holes Me for fastening screws (not shown), when the lower part 14a of this pump has been inserted into the casing of the internal combustion engine. The piston 24 is lifted from below in a conventional manner by a cam, and a return spring (not shown) moves it back in the opposite direction, that is to say downwards. Disposed above piston bush 22 is a threaded section 26 containing a spring-pressed valve 28 through which the fuel is fed into the previouslymentioned pressure conduit 20.

The admission conduit 12 is screwed into a threaded opening 14b of pump 14 and communicates with the annular suction chamber 14s of pump 14. The fuel passes from suction chamber 14s through a suction duct 22s of a piston bush into the operating chamber 22a therein. When piston 24 moves downwards fuel is drawn from the suction chamber 14s and during a subsequent upward movement a part of the indrawn fuel will flow back from the operating chamber 22a into the suction chamber 14s until the upper edge of piston 24 completely covers the suction duct 22s. The effective delivery stroke of the piston now begins and this continues until a control groove 24s at the periphery of the piston 24 re-establishes communication between the operating chamber 22a and the return flow opening 22s and permits a fresh backflow of the fuel until the end of the piston stroke. Of the total quantity of fuel which is drawn in by the piston, only a minor part (approximately one-sixteenth to one-fourth depending on the setting of the mixture and the rate of the operation of the engine) passes in this way to the injection nozzle, whilst the much greater part of the fuel is forcibly returned.

In order to prevent the returned fuel flowing into the admission conduit 12, for the reasons stated above, in accordance with the present invention the return flow conduit 18 is connected to the suction chamber 14s, with its opening into the latter arranged directly opposite the suction and return flow opening 22s. A nonreturn valve, in the form of a ball 30 seated at 18s at the end of the conduit 18 (FIG. 4), is disposed in the opening of the return flow conduit 18. The ball 30 is made of a synthetic material and has a hollow interior which is perforated by a number of ducts 30a, so that even when the ball 30 is applied against its seat there remains a small degree of communication between the suction chamber 14s and the return conduit 18 through at least one of these duets 30a. The travel of the valve ball 30 is limited by a cross pin 32 in conduit 18.

When fuel is introduced into the tank before the internal combustion engine is started, this fuel flows under the compulsion of the quantity of air therein through the filter 16 to pump 14, and after the valve ball 30, which is of light weight, is lifted, passes into the return flow conduit 18 and through the tank 10 until the complete system is evacuated of all remaining air and the tank is completely filled with fuel. During the operation, quantities of fuel overflowing into the suction chamber 14s will not be able to reach the admission conduit 12 because the flow resistance engendered there by the filter 16 is high. The free flowing fuel will, in fact, find the path of least resistance, lifting the valve 30 and flowing into the tank 10 through the return flow conduit 18.

During the suction stroke of piston 24, valve ball 30 is drawn against the valve seat 18s, the resistance to flow between the return flow conduit 18 and the suction chamber 14s then increasing to the extent that scarcely any extraction takes place from the return flow conduit 18. Practically the whole of the quantity of fuel educted is taken from the suction system 12, 16. As a result there is scarcely any turbulence or formation of bubbles in the complete system and the fuel always takes the path indicated by arrows in FIG. 1. For this reason the return flowing fuel, heated in the pump, travels a comparatively long distance in conduit 18 back to the tank 10 with cool fuel, and by this means is relatively well cooled and finally mixed with the cool quantity in the tank, thereby providing a continual cooling effect for the whole of the fuel in the system.

Because of the practically entire one-way flow, undesirable turbulence is eliminated or at least substantially reduced, and because of the continual cooling of the fuel the formation of bubbles, generally caused by overheating, is also prevented in the system. The delivery and quantity control therefore are performed with very considerable freedom from these undesirable factors and consequently with greater accuracy. Moreover in the arrangement according to the invention, plain and inexpensive conduits (without annular jointed pieces or hollow screws) can be used because no communicating conduit has to be opened for venting, the

venting of the whole system being automatically effected in the course of the filling of the tank with fuel.

The use of the valve 30 (or 30' as will be described) which always provides a slight leak has the further advantage that no column of fuel which would prevent the automatic venting procedure can be set up in the return flow conduit 18, as for example might possibly happen with a fully closing valve and in case of inadvertently emptying the tank 10 and the suction conduit 12.

Instead of using the hollow and perforated valve ball, use might alternatively be made of a ball 30 (see FIG. 5) which is externally smooth and a valve seat 18s with a number of grooves 18r therein to cater for a slight continuous communication between the return valve conduit 18 and the suction chamber 14s, as in the first example.

In the second embodiment illustrated in FIGS. 6 and 7, the elements 10 to 28 of the injection pump and its fuel conduit system have the same construction and function as in the first embodiment according to FIGS. 1 5, so they carry the same reference numerals. This makes it unnecessary to describe these elements in detail again.

In the second embodiment, however, in contrast to that first described there is no single and special connecting bore for the return flow conduit 18, but the connection nipple for the admission conduit 12 is made in such a way that it serves both for accommodation of the non-return valve, in the form of a ball 30', and for connection of the return flow conduit 18 as is described in more detail below.

The admission conduit 12 ends in an annular part 12a, which is pressed against a side surface of the injection pump 14 through the agency of a hollow connecting nipple which is screwed into a threaded bore 14b of the injection pump 14, with the interposition of two sealing rings 102. The fuel passes from conduit 12 through one or more traverse ducts 100a into the inner bore 1001' of the nipple 100 and thence to the suction chamber 14s of the injection pump 14. A valve seat 10% is provided for the ball 30 above the traverse duct 100a in the nipple 100, and a longitudinal groove 1000 in the inner wall of the nipple 100 ensures that a certain small quantity of fuel can flow through the valve seat even when the ball 30' is seated.

A connection piece 104 for the return flow conduit 18, which is provided with an axial bore 104b, and is screwed into the nipple 100, serves as an abutment for the lifted ball 30'. This abutment element has, at the end face thereof facing the ball 30 and serving as the abutment, a traverse groove 104a which ensures that even when the ball 30' abuts the nipple 104 the fuel can pass from the injection pump 14 into the return flow conduit 18 and back to the tank 10.

This embodiment also has the advantage that with the valve 30 which is always permeable to a slight extent at 1006, no column of fuel to prevent the automatic venting process can be set up in the return flow conduit 18, as for example would be possible in the case of a fully closed valve in the event of an unintentional emptying of the tank 10 and the suction conduit 12.

The main advantage of the present embodiment resides, however, in the fact that because of the special form of the junction nipple 100 the valve 30' and the return flow conduit 18 can be connected with the connection opening 14b of the injection pump which is also provided for the admission conduit 12, so that the assembly of the parts of the arrangement described, for example performed after construction of the pump, will call for no subsequent machining or special modification.

It is to be mentioned finally that the constructions illustrated and described represent only a few of the possible embodiments. The invention can be realised in other ways. Instead, for example, of using the springless valve we could under special operating conditions employ a lightly spring-loaded valve in the return flow conduit.

We claim:

1. In an injection internal combustion engine with at least one fuel injection pump, wherein the fuel passes by gravity flow from a supply container through an admission conduit to a suction chamber of the injection pump, the improvement comprising at least one return flow conduit separate from the admission conduit for superfluous fuel which has not been injected, said return flow conduit leading from the suction chamber of the injection pump to the supply container, and valve means for controlling flow through said return flow conduit to the supply container,'said valve means allowing even in its seated position a small flow of fuel such that at least a small flow of fuel is feasible between the return flow conduit and the suction chamber of the injection pump in each operational stage of the injection pump.

2. An injection internal combustion engine according to claim 1, wherein said injection pump is a piston injection pump, the piston of which is arranged in a piston bush provided with a return flow duct communicating with the suction chamber, the excess fuel not injected passing out through the return flow duct into the suction chamber of the pump, the return flow conduit being connected to the suction chamber, and the opening of the return flow conduit into the chamber being disposed approximately opposite the return flow duct in the piston bush.

3. An injection internal combustion engine according to claim 2 wherein said valve is a non-return valve and is located in the immediate vicinity of the mouth of the return flow conduit.

4. An injection internal combustion engine according to claim 3 wherein said non-return valve comprises a valve ball which cooperates with a valve seat in the return flow conduit, said valve ball having a plurality of narrow ducts at least one of which at any time provides a small conducting connection between the return flow conduit and the suction chamber when the valve ball is applied against the valve seat.

5. An injection internal combustion engine according to claim 3 wherein the non-return valve comprises a valve ball which cooperates with a valve seat in the return flow conduit, a number of grooves of small cross section being provided in the valve seat to furnish a small conducting connection between the return flow conduit and the suction chamber even when the valve ball is applied against its seat.

6. An internal combustion engine according to claim 4 wherein the valve ball has no return spring acting thereon and has a degree of play within the return flow conduit bounded by a limit abutment spaced from the valve seat.

7. An injection internal combustion engine as claimed in claim 4 wherein the valve ball is made of a synthetic material.

8. An injection internal combustion engine as claimed in claim 1 wherein said valve is of the nonreturn type, the valve seat of the non-return valve being provided in a coupling nipple which attaches the admission conduit to the casing of the injection pump, a coupling piece being provided on the coupling nipple for coupling the return flow conduit thereto, said coupling nipple having a portion spaced from the valve seat and acting as a limit stop for the non-return valve when the valve is in its raised condition.

9. An injection internal combustion engine as claimed in claim 8, wherein said non-return valve includes a valve ball associated with a conical valve seat in said couping nipple, at least one recess in the valve seat providing a conducting connection between the injection pump and the admission conduit, on the one hand, and the return flow conduit, on the other hand, even when the valve ball is seated.

10. An injection internal combustion engine according to claim 9 wherein at least one recess is provided in the portion of the coupling piece for the return flow conduit confronting said ball valve, this recess providing a conducting connection between the injection pump and the return flow conduit when the valve ball is in its raised condition. 

1. In an injection internal combustion engine with at least one fuel injection pump, wherein the fuel passes by gravity flow from a supply container through an admission conduit to a suction chamber of the injection pump, the improvement comprising at least one return flow conduit separate from the admission conduit for superfluous fuel which has not been injected, said return flow conduit leading from the suction chamber of the injection pump to the supply container, and valve means for controlling flow through said return flow conduit to the supply container, said valve means allowing even in its seated position a small flow of fuel such that at least a small flow of fuel is feasible between the return flow conduit and the suction chamber of the injection pump in each operational stage of the injection pump.
 2. An injection internal combustion engine according to claim 1, wherein said injection pump is a piston injection pump, the piston of which is arranged in a piston bush provided with a return flow duct communicating with the suction chamber, the excess fuel not injected passing out through the return flow duct into the suction chamber of the pump, the return flow conduit being connected to the suction chamber, and the opening of the return flow conduit into the chamber being disposed approximately opposite the return flow duct in the piston bush.
 3. An injection internal combustion engine according to claim 2 wherein said valve is a non-return valve and is located in the immediate vicinity of the mouth of the return flow conduit.
 4. An injection internal combustion engine according to claim 3 wherein said non-return valve comprises a valve ball which cooperates with a valve seat in the return flow conduit, said valve ball having a plurality of narrow ducts at least one of which at any time provides a small conducting connection between the return flow conduit and the suction chamber when the valve ball is applied against the valve seat.
 5. An injection internal combustion engine according to claim 3 wherein the non-return valve comprises a valve ball which cooperates with a valve seat in the return flow conduit, a number of grooves of small cross section being provided in the valve seat to furnish a small conducting connection between the return flow conduit and the suction chamber even when the valve ball is applied against its seat.
 6. An internal combustion engine according to claim 4 wherein the valve ball has no return spring acting thereon and has a degree of play within the return flow conduit bounded by a limit abutment spaced from the valve seat.
 7. An injection internal combustion engine as claimed in claim 4 wherein the valve ball is made of a synthetic material.
 8. An injection internal combustion engine as claimed in claim 1 wherein said valve is of the non-return type, the valve seat of the non-return valve being provided in a coupling nipple which attaches the admission conduit to the casing of the injection pump, a coupling piece being provided on the coupling nipple for coupling the return flow conduit thereto, said coupling nipple having a portion spaced from the valve seat and acting as a limit stop for the non-return valve when the valve is in its raised condition.
 9. An injection internal combustion engine as claimed in claim 8, wherein said non-return valve includes a valve ball associated with a conical valve seat in said couping nipple, at least one recess in the valve seat providing a conducting connection between the injection pump and the admission conduit, on the one hand, and the return flow conduit, on the other hand, even when the valve ball is seated.
 10. An injection internal combustion engine according to claim 9 wherein at least one recess is provided in the portion of the coupling piece for the return flow conduit confronting said ball valve, this recess providing a conducting connection between the injection pump and the return flow conduit when the valve ball is in its raised condition. 